Cyanocobalamin Dosage

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Usual Adult Dose for:

Usual Pediatric Dose for:

Additional dosage information:

Usual Adult Dose for Pernicious Anemia

Parenteral:
Initial dose: 1000 mcg intramuscularly once a day for 7 days. If there is clinical improvement and a reticulocyte response, 1000 mcg intramuscularly once every other day for 7 days, then once every 3 to 4 days for another 2 to 3 weeks is recommended. Most patients require monthly injections of 100 to 1000 mcg intramuscularly for life.

Nasal Spray or Gel:
Alternatively, cyanocobalamin (Nascobal) nasal spray or nasal gel 500 mcg intranasally to one nostril once a week may be administered to patients with pernicious anemia who require maintenance of normal hematologic status following intramuscular vitamin B12 and who have no nervous system involvement. However, if the patient is not adequately maintained with cyanocobalamin nasal, intramuscular vitamin B12 administration must be resumed.

Usual Adult Dose for B12 Nutritional Deficiency

Oral: 25 to 250 mcg once a day.
Nasal Spray or Gel:
(Nascobal) 500 mcg intranasally in one nostril once a week
(CaloMist) 25 mcg in each nostril once a day (total dose 50 mcg). May be increased to 50 mcg in each nostril once a day.

Usual Adult Dose for Schilling Test

1 mcg radiolabeled cyanocobalamin orally once after urinary voiding. A 24-hour urinary collection is immediately begun. At 2 hours an injection of cyanocobalamin 1,000 mcg intramuscularly is given to "flush" the patient of absorbed radiolabeled drug. The percentage of radiolabeled B12 excreted in the urine is a measure of how much labeled drug was absorbed. Normally 7% or more of a dose is excreted in 24 hours (< 7% may be considered a positive Schilling test).

Usual Pediatric Dose for Pernicious Anemia

Neonates and Infants: Intramuscular or Subcutaneous: 0.2 mcg/kg for 2 days, followed by 1000 mcg/day for 2 to 7 days; maintenance: 100 mcg/month.
Children: Intramuscular or Subcutaneous: 30 to 50 mcg/day for 2 or more weeks (to a total dose of 1000 mcg), then follow with 100 mcg/month.

Usual Pediatric Dose for B12 Nutritional Deficiency

Intramuscular or Subcutaneous: Initial: 0.2 mcg/kg for 2 days followed by 1000 mcg/day for 2 to 7 days followed by 100 mcg/week for a month or 100 mcg/day for 10 to 15 days (total dose of 1 to 1.5 mg), then once or twice weekly for several months. May taper to 60 mcg every month. For malabsorptive causes of B12 deficiency, monthly maintenance doses of 100 mcg have been recommended.

Renal Dose Adjustments

There are no data; however, there are reports of decreased renal elimination of the drug in patients with severe renal insufficiency.

Liver Dose Adjustments

Data not available

Dose Adjustments

Because cobalamin is inexpensive and has few side effects, larger doses may be given, such as 500 to 1000 mcg intramuscularly once a day x 2 weeks, then the same dose twice weekly x 4 weeks or until the hematocrit is normal, then the same dose monthly for life (every 2 weeks if neurological manifestations are present). Other suggested regimens include 1000 mcg intramuscularly once a week x 8 weeks, then once monthly for life.

Precautions

Low initial cyanocobalamin doses combined with potassium supplementation (as needed) may prevent a hypokalemia seen in patients with severe deficiency.

Patients with pernicious anemia are unusually subject to gastric polyps and have approximately twice the normal incidence of stomach cancer. Because of this, some experts recommend frequent stool guaiac examinations and further diagnostic studies when indicated.

In patients suspected of cyanocobalamin sensitivity an intradermal test dose of parenteral cyanocobalamin should be performed prior to initiating therapy with cyanocobalamin nasal spray or gel.

Dialysis

Data not available

Other Comments

Early neurological changes due to B12 deficiency can be rapidly and completely reversed if treatment is begun promptly within the first few weeks of illness. Late neurological changes, such as spinal cord dysfunction, may not improve, but disease progression is usually halted once B12 therapy is begun.

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